Can you put something more non-slip as footing in the crate? Like an old towel you don't care about or if you have some rubber mat- old door mat - anything but the slick plastic bottom of the crate.
In addition to a more non-slip type surface, I would give that baby a good bed of straw to rest in - a nice cushion to help catch itself and ease the impact. Speaking from experience, the "good" side will get tired supporting the injured side in the coming days. Enough times with the wing being put down for balance on a hard surface and you'll end up with damage there too. Think of it kind of like a padded room.
If you can find or order something like these, and attach them to the inside of the crate door, you'll find it so much easier to keep the crate dry (and therefore not stinky!!) A good investment for any time you've got a bird in a crate, especially one that's got mobility issues- more room in the crate with fewer things to navigate around.
https://www.amazon.com/dp/B01KZJIVEC/?tag=backy-20